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Phase transformations in bituminous coals under the influence of weak electric and magnetic fields

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Category: Solid-state physics, mineral processing

Last Updated on 17 October 2013

Published on 08 November 2012

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Authors:

G.G. Pivnyak, Academician of the National Academy of Science of Ukraine, Dr. Sci. (Tech.), Professor, State Higher Educational Institution “National Mining University”, Rector, Dnipropetrovsk, Ukraine

V.V. Sobolev, Dr. Sci. (Tech.), Professor, State Higher Educational Institution “National Mining University”, Professor of the Department of Building and Geomechanics, Dnipropetrovsk, Ukraine

A.O. Filippov, State Higher Educational Institution “National Mining University”, Research Fellow of the Department of Building and Geomechanics, Dnipropetrovsk, Ukraine

Abstract:

Purpose. To detect the emergence of mobile components in coal under the influence of electric fields and determine their possible effect on transition to the solid phase under action of a weak magnetic field.

Methodology. Samples were prepared from coal crushed to fractions of 200/100 mm with folowing characteristics: C – 86.6 %, N – 5.7 %, R0 - 1.03 %, Y = 18 mm, W = 1,1 %, Vdaf = 33.2 %, Qdaf = 36.4 MJ/kg. The maximum heating temperature during the electrophysical treatments did not exceed 400 K. The potential difference and the magnitude of the current were provided by the power source and were 1, 10, 100 V and 0.1 A, respectively. The current flowing through the heating coal excited the magnetic field strength up to 240 A/m in the sample. Duration of treatment of each sample did not exceed 4 hours. We used the following equipment: instrument of thermogravimetric analysis and differential scanning calorimetry, TGA/DSC METTLER TOLEDO, optical microscope LEICA DM ILM, a laser diffraction particle size analyzer SHIMADZU SALD-301V and calorimeter C-2000 IKA. Infrared spectra of coals have been made in the FTIR spectrometer FSM-1201 with the transmission in the spectral range of 400-5000 cm-1. X-ray diffraction studies on coal were carried out on DRON-3 installation.

Findings. Passage of a weak electric current triggers chemical reactions in the coal of the type ‘solid phase > gas’, increasing the concentration of paramagnetic centers (PMC) in aliphatic and aromatic structures. Under the influence of a weak magnetic field, the chemical reactions in the coal substance mainly aimed at increasing the number of solid phase and the formation of stable gas molecules resulting from recombination of free radicals.

Originality. In coals with a large number of aliphatic chains (low degree of coalification) under action of electric field the destruction processes of nanostructure occur as intensively as, for example, under heat, mechano-chemical and radiation-chemical transformations.

Practical value. The results of coal treatment in a weak electric field can be used in the processes of its decomposition and gasification, the influence of a weak magnetic field can be used to create a new way of ‘deactivation’ of the outburst hazard in coal.

References:

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